Purification of cyclic ketones



May l5, 1951 H. w. FLEMING 2,552,570

PURIFIcA'rIoN oF cycmc KEToNEs OBTAINED BY OXIDATION OF' HYDROCARBONS Filed July :50.1946

S MY E Patented May 15, 1951 UNITED STATES PATENT OFFICE PURIFICTION OF CYCLIC KETONES OBTAINED BY OXIDATION DROCARBONS Harold William Fleming, Bartlesville, Okla., assignor to Phillips Petroleum Company, a corporation of Delaware Application July 30, 1946, Serial No. 687,195

6 Claims.

This invention relates to the oxidation of cyclic hydrocarbons, and more particularly to the production of cyclic ketones by the oxidation of cycloparaiiins. In a speciiic aspect it relates to rthe removal of highly oxygenated organic comtion of cycloparaffins with air or with oxygen `is known to the art. It is also known that, particularly When such an oxidation process is ccnducted continuously, the effluent from the oXida tion zone contains, in addition to the desired oxidation product, highly active oxygenated compounds which appear 'to be organic peroxides. These highly oxygenated compounds are undesirable because, under the influence of heat, as for example, during fractionation of the oxidation effluent, at temperature of 100 C. they clecompose, often violently. The decomposition is accompanied by an exceedingly rapid evolution of heat, which makes temperature control difficult, and by some loss of the desired product. Since these highly active oxygenated compounds seem to be organic peroxides, they will be referred to as peroxides in this disclosure.

According to the prior art, these peroxides or the like have been removed by heating the Voxida tion elluent at carefully controlledtemperature at which the peroXides decompose non-violently. Since gas is liberated during the decomposition, pressure must also be carefully controlled. Such methods are undesirable because they tend Vto decrease product yield and to promote side reactions. Furthermore, they are not effective to remove peroxides completely without causing desired products to react further.

It is an object of the present invention to provide an effective method for removal of highly oxygenated products, such as organic peroxides, from reaction eiuents obtained by oxidation of cycloparaffins. It is a further object of the present invention to provide a process for removing peroxdes from the products of oxidation of cycloparaifins to form cyclic ketones and at the same time to increase the yield of cyclic ketones.

In accordance With the present invention, the peroXides 'are removed from the oxidation efuent by treatment With an aqueous solution of a reducing agent, such as a ferrous salt, a stannous salt, a chromous salt, a sulte, or a bisulte, that reduces peroxides. Treatment with aqueous ferrous sulfate produces, in addition, the effect, heretofore unexpected, of substantially increasing the yield of cyclic ketones. Although conditions for the ferrous sulfate treatment may vary greatly, treatment at about to 30 C. and atmospheric pressure is satisfactory. The concentration of the aqueous reducing agent may range from the minimum necessary to react with,v

Acompounds to organic acids.

all the peroxides, to that necessary fora saturated aqueous solution. When a solution of a metal salt is used, it is preferable that the solution contain suiicient acid, preferably sulfuric, to prevent hydrolysis. Suilicient acid is present when the solution has a pH below about 3. In general, a pH of about` l to 2.5 ispreferred.

The invention maybe described in greater detail with reference to the accompanying drawing, which is a 'schematic flow diagram of one arrangement of apparatus suitable for practicing the invention.

Cyclopentane and air enter reactor 4 through inlets 2 and 3, respectively. Reactor 4 is prefer- `ably so constructed that the influent air is divided into small bubbles, as by the use of a perforated distributor, which contact the cycloparailn, cyclopentane for example, Oxidation catalysts such as lead and mangenese acetates may be present if desired. Reaction conditions are, approximately: temperature, to 200 C.; pressure, 100 to 500 p. s. i.; residence time, 30 to 100 minutes; volumes of air per volume of liquid cyclopentane, 50 to 200. The gaseous eilluent passes through conduit I to partial condenser 3, in which normally liquid material is liqueed and from Which the liquefied material is passed to settler 6 through conduit 9. Normally gaseous material is 'withdrawn from the system through outlet I0. The liquid effluent from reactor 4 is passed through conduit 5 to settler 6, in which it separates into a heavier or aqueous phase and a lighter or organic phase. The aqueous phase, which contains, in addition to Water, Water-soluble oxygenated organic compounds, is withdrawn through outlet I I, and may be treated, by means not shown, to convert the Water-soluble organic The organic phase is passed through conduit I2 to caustic Washer i3, in which dissolved acids are removed by Washing with aqueous alkali. The Washed organic phase is passed through conduit I4 to treater I5, in which it is intimately contacted with aqueous ferroussulfate, or other suitable aqueous reducing agent, which enters through conduits 20 and lf3. Since the peroxide-ferrous sulfate reaction is exothermic, it is desirable that treaterl I5 be provided with suitable cooling means, not shown in the drawing, in order to maintain the temthe concentration of the ferrous sulfate solution gradually increases; therefore water is continuously added tothe solution through inlet 2 I. This water preferably contains some acid, preferably sulfuric acid, to prevent hydrolysis of iron salts. In order to prevent undesirablyhigh accumulation of ferrous sulfate solution in the system, part of the aqueous phase withdrawn from settler I1 through conduit I8 is withdrawn from the system Ythrough outlet 22. The substantially peroxide-free organic phase separated in settler I1 is passed through conduit 23 to fractionator 24, which, in practice will usually toa series of two separate fractionating colums. In fractionatorV 24 the following fractions are separated: a relatively low-boiling fraction comprising mainly unreacted cyclopentane, which is recycled through conduit 25 to reactor ll; an intermediate fraction comprising mainly cyclopentanone, which is with- It may be noted that, although the resurts in Examples I and II were obtained by simple batch drawn, as the main product of the process,

through outlet 26; and a relatively high-boiling kettle product comprising cyclopentanol, which is `withdrawn through outlet 2'I. The last-named fraction may be converted to cyclopentanone by Ydehydrogenation in means not shown in the drawing.

' Example I In each of three runs, cyclopentane was oxid- .ized by air in a reactor similar to that previously described. The total oxidation product was allowed to stand until the aqueous phase had separated from the organic phase. Unreacted cyclopentane was separated from the organic phase by fractionation. The cyclopentane-free product was then treated with saturated aqueous ferrous sulfate containing sufficient sulfuric acid to prevent hydrolysis of iron salts. The peroxide content of the treated and the untreated organic phase was determined by titration of samples with standard ceric sulfate solution. The fol- It is noteworthy that, in Run 3, the ferrous sulfate treatment eiected simultaneously a 99 per cent removal of peroxides and an 8 per cent increase in the yield of cyclopentarione.

Example II In two runs similar to those described in Example I, methylcyclopentane was oxidized with air to rnethylcyclopentanone. The product was freed from unreacted methylcyclopentane by fractional distillation. The methylcyclopentane-free product was treated with ferrous sulfate solution as previously described. The following data were obtained:

Peroxides ni Product, Calculated as H2O2,

wt. Per Cent Run ' Before After FeSO4 FeSO4 Treatment Treatment treatments with ferrous sulfate, the lowest peroxide removal was 96 per cent (Run 4).

I claim:

1. A process for the production of cyclic ketones substantially free from organic peroxide impurities which comprises oxidizing a cycloparaiiin with oxygen in the presence of an oxidation catalyst; separating from the products of reaction an organic phase comprising cyclic ketones, cyclic Y alcohols, unreacted cycloparaii'in, and Vorganic acids and peroxides as'impurities; washing said organic phase with alkali to neutralize said acids; contacting the washed product with an aqueous ferrous sulfate solution containing sufficient sulfuric acid to preventhydrolysis of said ferrous sulfate; separating the resulting mixture into an organic phase and an aqueous phase'containing ferric sulfate; recovering from the thus separated organic phase cyclic alcohols, Vunreacted cycloparafn and cyclic ketones resulting from said oxidation ofa cycloparain and from said reaction with ferrous sulfate; recycling said recovered cycloparafn to said oxidation step; Icontacting at least a portion of said aqueous phase containing ferric sulfate with iinely divided iron to regenerate ferrous sulfate from saidferric sulfate; and introducing'said regenerated ferrous sulfate, water and sulfuric acid to said step wherein the alkali washed-organic phase is contacted with an aqueous ferrous sulfate solution.

2. A process according to claim 1 wherein the aqueous solution of ferrous sulfate is acidied to a pH in the range of 1 to 2.5.

3. A process according to claim 1 wherein the aqueous ferrous salt solution is acidied to a pI-I below 3.

4. A process according to claim 1 wherein the the oxidation reaction mixture is contacted with a ferrous salt at a temperature of 0 to 30C. and at atmospheric pressure.

5. A process according to claim 1 wherein the the cycloparafn is cyclopentane and cyclopentanon-e is produced as a product of the process.

6. A process according to claim 1 wherein the cycloparailin is methylcyclopentane and methylcyclopentanone is produced as a product of the pIOCeSS.

HAROLD WILLIAM FLEMING.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS OTHER REFERENCES Hock: Ber. 72B,15628 (1939) I-Iock et al.: Berichte, Vol. 75, pages 1051-1054, (1942); vol. 76, pages 1130-1131, (1943); vol. 76, pages 169-172 (1943) Y 

1. A PROCESS FOR THE PRODUCTION OF CYCLIC KETONES SUBSTANTIALLY FREE FROM ORGANIC PEROXIDE IMPURITIES WHICH COMPRISES OXIDIZING A CYCLOPARAFFIN WITH OXYGEN IN THE PRESENCE OF AN OXIDATION CATALYST; SEPARATING FROM THE PRODUCTS OF REACTION AN ORGANIC PHASE COMPRISING CYCLIC KETONES, CYCLIC ALCOHOLS, UNREACTED CYCLOPARAFFIN, AND ORGANIC ACIDS AND PEROXIDES AS IMPURITIES; WASHING SAID ORGANIC PHASE WITH ALKALI TO NEUTRALIZE SAID ACIDS, CONTACTING THE WASHED PRODUCT WITH AN AQUEOUS FERROUS SULFATE SOLUTION CONTAINING SUFFICIENT SULFURIC ACID TO PREVENT HYDROLYSIS OF SAID FERROUS SULFATE; SEPARATING THE RESULTING MIXTURE INTO AN ORGANIC PHASE AND AN AQUEOUS PHASE CONTAINING FERRIC SULFATE; RECOVERING FROM THE THUS SEPARATED ORGANIC PHASE CYCLIC ALCOHOLS, UNREACTED CYCLOPARAFFIN AND CYCLIC KETONE RESULTING FROM SAID OXIDATION OF A CYCLOPARAFFIN AND FROM SAID REACTION WITH FERROUS SULFATE; RECYCLING SAID RECOVERED CYCLOPARAFFIN TO SAID OXIDATION STEP; CONTACTING AT LEAST A PORTION OF SAID AQUEOUS PHASE CONTAINING FERRIC SULFATE WITH FINELY DIVIDED IRON TO REGENERATE FERROUS SULFATE FROM SAID FERRIC SULFATE; AND INTRODUCING SAID REGENERATED FERROUS SULFATE, WATER AND SULFURIC ACID TO SAID STEP WHEREIN THE ALKALI WASHED-ORGANIC PHASE IN CONTACTED WITH AN AQUEOUS FERROUS SULFATE SOLUTION. 